Like Banksy, France’s mystery ‘Invader’ marks cities with art. He could surprise the Paris Olympics

A mosaic by French artist Invader (top right) is seen on a street of Paris For the Paris Olympics, it could almost be a new sport: Score points by hunting down mosaics that a mystery artist who calls himself “Invader” has cemented to walls across France’s capital, the world and even had carried aloft to the International Space Station. Vincent Giraud, one of the artist’s Parisian fans, is already an avid player. He downloaded Invader’s addictive “Flash Invaders” mobile-phone game that awards points to users who find and photograph the colorful and quirky pieces of pixelated art. Quickly hooked, Giraud has in just a year already tracked down 1,565 of them, accumulating so many points that he has rocketed into the leaderboard’s top 1,000, out of more than 360,000 players. “In a few months I found and flashed all those in Paris,” says Giraud, game-name Vince-Vader. Hunting for Invader mosaics, looking up and around for them on walls, pavements, bridges and even atop the Eiffel Tower, is “another way of discovering the city.” Put simply: When Olympic visitors flock in their millions to Paris for the July 26-Aug. 11 Games, they’ll be crowding onto the turf of France’s most international,...